Video surveillance, e.g., security, systems are often deployed in and around buildings as well as in metropolitan settings. Example buildings and metropolitan settings include schools, government buildings, commercial buildings, residential buildings, roads and highways, and town and city centers.
These video security systems typically include surveillance, e.g., security, cameras that connect via a security network to a control system. Additional components include network video recorder (NVR) systems and monitors for displaying images such as video from the security cameras.
The security cameras typically have a lens and image sensor that are fixed, adjustable, or motorized. A fixed security camera will have the lens and imager system permanently fixed in a set position (i.e., lens and imager system cannot change position with respect to camera body). On the other hand, an adjustable security camera's lens and imager system is movable with respect to camera body (e.g., installer can move the lens and imager system to different positions) so that it can be pointed down a hall or at a door, for example. A motorized security camera, such as a pan-tilt-zoom (PTZ) security camera, utilizes motor(s) to automatically move the lens and imager system to different positions usually under operator or automatic control.
Fixed security cameras often have wide angle lens systems to compensate for their inability to be aimed. An extreme example of a wide angle camera is a fisheye camera. The fisheye security camera uses an ultra-wide-angle fisheye lens to form an image on the image sensor.
The fisheye security cameras are typically used in situations in which there is a need to capture a wide field of view in a single image. They also tend to be more mechanically robust than adjustable cameras. The fisheye security cameras provide this wide field of view by utilizing the fisheye lens to provide, for example, between 180 degrees and 360 degrees of surveillance range. Due to the wide field of view, the raw image captured by the imager chip is distorted, however.
The installation process of a fixed security camera (e.g., fisheye security camera) in a video security system involves several steps. An installer mounts the fisheye security camera at a desired location that allows for the fisheye security camera to capture a wide area of interest. For example, the fisheye security cameras are typically installed in a wall mode orientation or ceiling mode orientation. In the wall mode orientation, the optical axis of the camera's lens system extends in a horizontal direction. This is common when the fisheye security camera is installed on a wall of a building or room. In the ceiling mode orientation, the optical axis of the camera's lens system extends in a vertical direction. This is common when the fisheye security camera is installed on a ceiling of a room or hallway or on a mounting arm extending from a building, lamppost or other structure. In either mode, the camera should usually be leveled to ensure good image orientation. Then, the installer will usually program the video security system with the fixed security camera's orientation.
In general, there is distortion processing software to correct a distorted or warped image by de-warping the image. In particular, this distortion processing software uses image processing algorithms or models corresponding to the lens being used (e.g., fisheye lens) and information on the camera's orientation mode to correct and rotate the distorted image.